Method of cleaning strip



1941- E. A. MATTESON ETAL 2,259,260

METHOD OF CLEANING STRIP Filed Oct. 30, 1939 2 Sheets-Sheet 1 INVENTORS F! WIN A. NATTESO/V k/EZ B. .BO W/1A/V ATTORNEYS Oct. 14,1941.

E. A. MATTES ON ETAL METHOD OF CLEANING STRIP 1939 2 Sheets-Sheet 2 Filed Oct. 30

INVENTOIE Patented Oct. 14, 1941 ICE 7 METHOD OF CLEANING STRIP ElwinAJIatteaon andKielILBowman, Y

town, Ohio, Engineering corporation of Ohio assignors ,to C mpany,

The Aetna Standard Youngstown, Ohio, a

Applicationbctober :0, 1m, Serial in. arm

Claims. (01. -409). This invention relates to metal cleaning and more particularly to an improved method of and apparatus for removing oil or the like from strip steel or other elongated metal articles.

In the cold rolling of strip steel oil is applied to the surfaces of the metal for purposes of lubrication and to preventoxidization of the surface of the metal. This oil may be either mineral or vegetable, palm oil being commonly used, and its removal after completion of the rolling operation presents a serious problem particularly in connection with strip which is to be used for P rcelain enameling or lithograph work.

After rolling the strip is usually annealed by \eration, leaving particles of carbonaceous ma- If there is any oil on the' terial in or on the metal. Such particles prevent the proper adherence of lithographic or enamel coatings and thus the complete removal --I"igure 2 is a diagrammatic side elevational view, partly in section, of a strip cleaning apparatus adapted to carry out the steps of our method but omitting the electricalstrip heating equipment.

Figure 3 is a plan view of the apparatus shown in Figure 2.

Referring particularly to Figure 1, a coil of strip I, which has come from the cold rolling mill and has a coating of oil, is illustrated at the left hand side of the view. This strip passes through the alkali scrubber indicated generally at S and which includes four staggered supporting rolls 2, 3, 4 and 5, and four rotary scrubbing heating to a sumciently high temperature in an .15

of all oil from the surfaces of the strip is of great importance.

It has previously been proposed to pass the by means of hot alkali solutions whereby oil will be substantially entirely removed and whereby the strip may be passed through the solution at high speed without reducing the cleaning efllciency. Other objects of our invention include the provision of an improved strip cleaning procedure which is simple and economical and which can be operated continuously for long periods of time without excessive attention; and the provision of an improved apparatus for carrying out the steps of our strip cleaning method.

The above and other objects of our invention will appear from the following description of certain preferred embodiments thereof, reference being had to the accompanying drawings, in which:

Figure 1 is a diagrammatic side elevational view, partly in section, of an apparatus for carrying out our improved cleaning procedure, the apparatus including electrical means=for heating the strip.

brushes 6, .1, 8 and 9. Adjacent each of the scrubbing brushes is a hot alkali supply pipe Ill. The scrubbing brushes and the pipes in extend across the entire width of the strip and the pipes are provided with perforations or nozzles adapted to direct a plurality of high velocity jets of hot alkali against the surface of the strip adjacent the scrubbing brushes. As shown by the arrows in Figure 1, the direction of rotation 01' the scrubbing brushes 8, I, 8 and O'is preferably opposed to the direction of movement of the strip through the apparatus. It will be 1mderstood that suitable feed rolls will be provided to move the strip through the apparatus at the desired rate of speed but such rolls are not shown as they form no part of the present invention.

.In thepreferred operation of our invention hot alkali solution (for example, soda ash and/or other alkali in water) at a temperature of about F. is discharged upon the strip through the pipes Ill. The scrubbing brushes 6, I, 8 and l, and the hot alkali remove the surface oil from the strip as it passes through the unit 8. However, the scrubbing operation usually does not completely remove the oil which has been absorbed into the pores of the metal and in order to remove this oil we pass the strip over a guide pulley Ii into the tank I! containing a hot alkali bath II. Guide rolls I maintain the strip submerged beneath the surface oi. the alkali and a roller i5 guides the strip at the exit end of the tank [2. A hood it, having an outlet ll, 'may be provided to collect and carry away vapors and fumes which arise from the bath It. In order to maintain the hot alkali bath ll atthe desired temperature, 1. e. from about F. to 230 F., heating pipes I 8 may be provided in the bottom of the tank I! and heated by steam or other suitable heating source.

As the cleaning and emulsifying action of the 55 hot alkali on the oil varies approximately as the square of the temperatureoi the alkali bath, we provide means in the tank" for electrically heating the reach of strip which is submerged in the bath is to a temperature somewhat above the boiling point of the bath, for example, approximately 250 F. This heating of the strip as it passes through the alkali bath is causes the solution immediately adjacent the surface of the strip to boil actively and the accompanying heat and agitation materially increase and facilitate the emulsification and removal of oil from the pores of the metal.

In order to apply the necessary current to the strip we preferably employ the arrangement shown in Figure 1, although it will be understood by those skilled in the art that various other hook-ups and contact means may be employed. In Figure 1 a central electrode roller l9 engages the strip opposite the central guide roll l4. Suitable means, not shown in detail, are provided for holding the roll is in engagement with the strip and electrical connections extend from the roll l9 through the wall of the tank l2, an insulator being indicated at 20, to one terminal of the secondary 2| of the transformer T.

, The opposite terminal of the secondary 2i is grounded at 22 and electrical connections lead from said opposite end of the secondary to the strip engaging electrode rolls 23 and 24. These rolls are preferably located opposite the end guide rolls l4 andare held against the strip by any suitable mechanism. Conductors 25 and 26 lead to the secondary 2| of the transformer T and the contact rollers 23 and 24 and their electrical connections are grounded at 21 and 28 respectively.

The transformer T is adapted to reduce the normal line voltage to a low value, for example 6 volts, and sufiicient current is applied from the center terminal roller l9 toeach of the end terminals 23 and 26 to heat the reaches of the strip indicated at i and l up to approximately 250 I stantially, for example to about 150 F. This heated strip then enters the bath l3 and its temperature need be raised only a relatively small amount in order to get it up to the preferred value,- i. e. the point at which the alkali will boil when in contact with the strip, and thus insure the most effective emulsifying and removal of the oil from the pores of th metal. The scrubber S performs two functions therefore, first to remove the larger portion of the surface film of oil from the strip, and second to preheat the strip so that it may readily be brought up to the desired temperature in the emulsifying bath I3.

The scrubber action alone will remove surface oil but does not aifectively remove oil from the pores of the metal. The immersion of a strip in a bath of alkali, without previous scrubbing of the strip, is also ineffective to remove the oil thoroughly because such immersion does not remove the relatively thick surface oil with saidcient rapidity to permit of practical operation. Our improved procedure in which the strip is first scrubbed and preheated by high velocity hot alkali jets and then passed through an even hotter alkali solution where the alkali has free access to the oil in the pores of the metal with the result that the oil in the pores is emulsified and floats to the surface of the bath from which it may be skimmed or otherwise removed, re-

trouble.

vAfter passing out of the bath l3 and over the v roller IS the strip is preferably rinsed by means of high pressure water sprays inthe rinser R. The water spray nozzles are indicated at 29 and guide rolls 30 direct the strip through the rinser. Immediately following the rinser is a dryer D of any suitable type which evaporates any rinse water remaining on the strip and the oilfree strip will emerg from the dryer ready to be annealed or otherwise processed.

A modified form of our invention is illustrated in Figures 2 and 3, in which the coil of strip 3| passes through a scrubber S, substantially similar to the scrubber S and comprising supporting rolls 32, brushes 33 and high pressure hot alkali jets 34. ing pipes 36 and the strip is guided by rollers 31,

38, 39 and 40 so that it passes belowthe surface I of the alkali bath 4| for a distance sufficient to permit the hot alkali bath to emulsify the oil which remains in the pores of the metal after the scrubbing operation is carried out in the unit S. In this form of our invention the electrical heating of thestrip as it passes through the hot alkali bath 4i is not employed as, in some instances and-with some types of oil, the additional emulsifying and cleaning action caused by the active boiling of the alkali solution immediately at the surface of the strip may not be required. The washer or rinser R is sub.- stantially similar to the rinser R and the dryer D is the equivalent of the dryer D.

The alkali baths i3 and 4| may be maintained substantially at the boiling temperature of the superheated steam in the pipes 36 and we have found that the cooperative results of this bath with the combined scrubbing and preheating which occurs in the scrubber S and which removes the surface film of oil in such a manner that the hot bath of alkali in the tank can have access to the oil in the pores of the metal, produces cleaning results impossible to obtain with previously proposed methods and apparatus. Our electrical heating procedure for raising the strip to a temperature higher than the boiling point of the solution permits an agitation and extremel effective release of emulsified oil from the pores of the strip in the bath.

The entire system is adapted for continuous operation and, although we have described in considerable detail the illustrated embodiments of our improved apparatus and certain preferred procedures for carrying out our method, it will be understood by those skilled in the art that variations and modifications may be made without departing from the spirit of our invention. We do not, therefore, wish to be limited to the particular form herein described but claim as our invention all embodiments thereof coming The hot alkali tank 35 containing heat said moving preheated strip to remain in the bath long enough to emulsify and remove oil from the pores of the metal surfaces, removing said strip from the bath, and subjecting said strip to a water rinse.

2. A process of continuously cleaning longitudinally moving strip metal or the like which includes the steps of preheating the moving strip and causing high velocity hot alkali solution to impinge upon both sides of th moving strip, scrubbing the surfaces of both sides of the strip in the presence of said hot alkali solution whereby surface 011 is removed from the strip, passing said preheated strip into and through a hot alkali bath, maintaining the temperature of said bath between about 190 F. and 230 F. whereby oil in the pores of the surface of said strip is emulsified and removed, and rinsing said strip to remove the alkali therefrom.

3. A process of continuously cleaning longitudinally moving strip metal which includes the steps of passing the strip through an alkali bath, and. while the strip is submerged in the bath, generating heat in the strip itself whereby coiling of the alkali bath will occur adjacent the surfaces of the strip.

4. A process of continuously cleaning longitudinally moving strip metal which includes the steps of passing the strip through an alkali bath, and, whil the strip is submerged in the bath, causing an electric current to flow in a reach the strip which is submerged in said bath whereby said reach of strip is heated to a temperature above about 200 F.

5. A process of continuously cleaning longitudinally moving strip metal which includes the steps of causing high velocity Jets of alkali solution at a temperature of F. or higher to impinge against both sides of the moving strip whereby said strip is preheated, scrubbing both sides of said strip in the presence of said hot alkali solution, passing said preheated strip through a hot alkali bath, maintaining the temperature of said bath between about F. and 230 F., generating heat by electrical resistance in the reach of strip in said alkali bath, arr-:51 rinsing said strip to remove alkali therefrom.

ELWIN A. MATTESON. BEL B. BOWMAN, 

